<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1 {
            width: 100px;
            height: 100px;
            background: red;
            display: block;
        }

        .box2 {
            width: 100px;
            height: 100px;
            background: blue;
            display: none;
        }

        .box3 {
            width: 100px;
            height: 100px;
            background: yellow;
            display: none;
        }
    </style>
</head>

<body>
    <div class="contaner1">
        <button>按钮一</button>
        <button>按钮二</button>
        <button>按钮三</button>
        <div class="box1">1</div>
        <div class="box2">2</div>
        <div class="box3">3</div>
    </div>
    <button class="next">下一页</button>

    <div class="contaner2">
        <button>按钮一</button>
        <button>按钮二</button>
        <button>按钮三</button>
        <div class="box1">1</div>
        <div class="box2">2</div>
        <div class="box3">3</div>
    </div>
    <script>
        // 面向对象：简单的程序 面向过程；
        // 面向对象：需求复杂(属性方法比较多) 涉及对象较多 。
        // 需求一：写一个选项卡；


        function tab(btns, divs, isone) {
            btns.forEach((btn, key) => {
                btn.onclick = function () {
                    switchTab(key);
                }
            })


            // 可以切换到指定的key的div上
            function switchTab(key) {
                divs.forEach((div, index) => {
                    if (key == index) {
                        div.style.display = "block";
                    } else {
                        div.style.display = "none";
                    }
                })
            }
            
            // 不好
            if(isone){
                // 第一个选项卡
                var nextBtn = document.querySelector(".next");
                var num = 0;
                nextBtn.onclick = function(){
                    switchTab(num);
                    num++;
                    if(num>2){
                        num = 0;
                    }

                }
                

            }

            


        }

        var btns = document.querySelectorAll(".contaner1 button");
        var divs = document.querySelectorAll(".contaner1 div");
        tab(btns, divs, true);

        var btns2 = document.querySelectorAll(".contaner2 button");
        var divs2 = document.querySelectorAll(".contaner2 div");

        tab(btns2, divs2);



    </script>
</body>

</html>